Tianyi Cui
da5a1fc811
Skipped matrix jobs never expand matrix display values, so let GitHub use stable job identifiers. Bind optimized jobs to pull requests and the three serial references to master pushes.
4.8 KiB
Agent Note: Serial cross-platform CI reference
Status: implemented
English | 中文
Problem
The pull-request workflow reaches its latency targets by scheduling the complete primary Node inventory concurrently inside one larger runner. The optimized scheduler still should not be its own only completeness oracle: a defect in its gate inventory or dependency graph could omit work while the optimized job stays green.
Encoding the one-minute non-Windows target and three-minute Windows target as job timeouts creates a separate failure mode. Hosted-runner startup and performance vary, so a correct gate can be cancelled at the target boundary before it emits useful diagnostics. The performance objective needs measurement against GitHub timestamps, while correctness needs enough time to finish.
Reviewers also need a direct answer to a simpler question: what happens when the repository's complete primary Node CI aggregate runs without matrix selection, shard variables, or concurrent gates on each selected hosted operating system?
Decision
CI gives pull-request and master-push events complementary responsibilities. Pull requests run only the optimized larger-runner and compatibility jobs. A push to master skips those jobs and runs three explicit references named serial / linux, serial / macos, and serial / windows. They intentionally duplicate their short checkout, runtime setup, and immutable install sequences instead of hiding the operating systems behind a matrix or reusable workflow. workflow_dispatch is reserved for runner benchmarks.
Each reference job runs pnpm run check:ci without any shard selector. DSH_GATE_CONCURRENCY=1 makes the top-level aggregate execute one ready gate at a time; coverage, snapshot replay, built-bin smoke, and publication validation also receive worker counts of one. The three operating-system jobs may run beside one another, but each host's repository gates are serial and complete. Linux installs bubblewrap before replaying snapshots, and Windows enables Developer Mode before installing the symlinked workspace.
Master reference jobs are diagnostic and do not participate in the pull request's required all checks passed result. A pull request runs only the optimized jobs; a master push runs only the three serial references. The one-minute non-Windows and three-minute Windows objectives are evaluated from completed hosted-job timestamps and reported as measurements; they are not timeout-minutes values.
The portable reference uses GitHub's standard ubuntu-latest, macos-latest, and windows-2025 labels. A higher-core hosted runner remains a possible future benchmark, but it is not the default: larger runners require organization-owned labels and provisioning, while a reference oracle should remain runnable without repository-external runner configuration. Provisioning one later can change the performance experiment without changing this correctness baseline.
Alternatives considered
- Set each timeout equal to its latency target - rejected because scheduling variance would cancel correct work and suppress the evidence needed to diagnose a regression.
- Trust only the concurrent primary inventory - rejected because scheduling and validation share implementation assumptions; a serial aggregate is an independent completeness check.
- Run the serial references on every pull request - rejected because they deliberately trade wall time and runner consumption for simplicity and are not needed in the fast feedback loop.
- Use one operating-system matrix - rejected because three named jobs make the reference surface visible without another selection mechanism.
- Run the serial reference on larger runners - rejected because the reference is the portable fallback for the organization-specific pull-request topology. The fast pull-request path uses provisioned larger runners; the serial master path keeps standard labels.
Consequences
The workflow contains duplicated setup steps and a master reference run can take much longer than the optimized pull-request path. That duplication is deliberate: reviewers can inspect each operating system's complete command without resolving a matrix or concurrent scheduler.
The reference may expose platform failures that the optimized blocking set does not yet claim to support, especially on Windows. Such a failure is evidence about current cross-platform behavior rather than a reason to weaken or silently skip the aggregate.
Removing strict duration timeouts means a latency regression is observed rather than automatically cancelled. Hosted measurements must therefore accompany performance changes, while the completed logs retain the information needed to optimize the slow lane.